DYNAMICS OF MEGASYSTEMS IN GEOCHEMISTRY: FORMATION OF BASE MODELS OF PROCESSES AND SIMULATION ALGORITHMS

Abstract

On the basis of thermodynamic-potential minimization, an approach to construction and investigation of simulation models of dynamic megasystems has been developed. Dynamic megasystems are chemically interacting natural and geotechnical systems (reservoirs) connected with each other by direct, reverse, and through flows of matter and energy. The structure of a simulation model is formed by combining basic constituents and directive parameters. Systems and connecting flows may be aggregated into a single physicochemical object - a megasystem - in different ways. The evolution of megasystems can be calculated by two algorithms. In the first algorithm, two operations are performed in time unit: calculation of simultaneous equilibria in all systems and transfer of matter with flows in accordance with the specified matrix of macrokinetic coefficients of transfer. In the second algorithm, the evolution of megasystems in time and space proceeds in cycles. In each cycle, equilibrium calculation and matter transfer are performed consecutively from system to system in accordance with the system numbering and matrix of macrokinetic coefficients. The number of time units is equal to the number of the systems of a megasystem. The cycle of the latter algorithm ends in the system with the greatest number, and the next cycle begins in the first system. The most important peculiarity of both the algorithms is separation and division of flows into groups of mobile phases. Flows of aqueous solutions, gas mixture, solid substances (such as aeolian dust, furnace charge, mineral suspension in water), liquid hydrocarbons, organic matter, etc. can be transferred from system to system. Each group of mobile phases has a matrix of macrokinetic coefficients. If required, macrokinetic coefficients can be recalculated by built-in algorithmic operators in the intervals between time units. The proposed approach is illustrated by two examples. In the first one, the resistance of Lake Imandra (north of the Kola Peninsula) to pollution with nepheline-apatite production waste was investigated by an integral physicochemical index - pH of water, depending on the waste volume. In the second example, matter redistribution in the Al2O3-SiO2-H2O megasystem was studied. This redistribution is caused by an external energetic effect - formation of a stationary nonisothermal profile at T = 300-440°C and P = 3 kbar. The simulation results are compared with Vidal's experimental data. The formation procedures and simulation algorithms for dynamic megasystems were realized in the form of the «Reservoir dynamics» module included into the program complex Selektor-S designed in 1997. It may be used for solving different scientific problems as well as in engineering and educational institutions.